Electric resistance-conductor



No Model.)

H. G. ONEILL 82; H. B. GALE. ELECTRIC RESISTANCE CONDUCTOR.

No. 599,352. Patented Feb. 22, 1898.

BY W

ATTORNEYS.

UNITED STATES PATENT OFFICE.

HENRY G. ONEILL, OF BROOKLINE, AND HORACE B. GALE, OF BOSTON,MASSACHUSETTS, ASSIGNORS TO THE AMERICAN ELECTRIC HEATING CORPORATION,OF BOSTON, MASSACHUSETTS.

ELECTRIC RESISTANCE-CONDUCTOR.

SPECIFICATION forming part of Letters Patent No. 599,352, dated February22, 1898.

Application filedlll'anuary 4, 1897. Serial No. 617,924. (No model.)

To all whom it may concern.-

Be it known that we, HENRY G. ONEILL, residing at Brookline, in thecounty of Norfolk, and HORACE B. GALE, residing at Boston, in the countyof Suffolk, State of Massachusetts, citizens of the United States, haveinvented a new and useful Improvement in Electric Conductors and Processof Forming the Same, of which the following is a specification.

This invention relates to electric conducting devices adapted to resistthe oxidizing influences of air, moisture, and other oxidizing agentsand also to withstand very high temperatures, such as a red or whiteheat, without suffering any permanent change.

The main object of the invention is to produce a conducting device ofmoderate cost which shall have the qualities above indicated, which, inaddition, may be made of high specific resistance as compared to otherdevices possessing the qualities aforesaid, (such as platinum wire,) sothat a great resistance maybe easily concentrated in a small space, andwhich under such conditions may be given sufficient mechanical strengthto enable it to endure the rough treatment to which it may be subjectedin use.

Conducting devices made in accordance with this invention are applicableto a wide range of uses, and are especially adapted for use asresistances to be interposed in an electric circuit either for thepurpose of controlling the current therein, as in rheostats, or

for the generation of heat, more particularly where very hightemperatures are required, as in branding, cauterizing, or theproduction of light by incandescence.

The conducting element in this invention consists, essentially, of oneor more of the permanent refractory oxids, the general term oxic as usedherein, being understood to include both the simple combinations ofoxygen with the basic or metallic elements separatelysuch as oxid ofcopper, oxid of silicon, or silica-and also the more complexcombinations of oxygen with two or more such elements together forexample, kaolin or clay, often described as a silicate of alumina, whichis a combination of oxygen and the two basic elements, silicon andaluminium.

Different oxids have different degrees of electrical conductivity, theirconductivity in creasing generally with an increase of temperature, andby mixing the oxids of higher with those of lower conductivity invarying proportions compounds are produced having a wide range ofconductivity and resistance suitable for different special purposes.

Among the oxids suitable for the purposes of the present invention theprotoxid of vanadium appears to be the highest in conductivity, whilesilica is among the lowest, being classed as an insulator at ordinarytemperatures. By fusing these together in proportions varying betweenthe pure protoxid of vanadium to a composition containing onethird ofsilica a range of intermediate conductivities is obtained sufficient tomeet the ordinary demands of practice. The practice of the invention,however, is not restricted to the employment of these or any particularoxids or compositions thereof, as a great va-' riety of them maybe usedin adapting the device to special requirements. Almost any othermetallic oxid may be employed in greater or less proportion incomposition with that of vanadium, for example, the prin-= cipal effectof the substitution of one for another being generally a change in theresistance of the compound. Among the oxids which we have employed asingredients of the conducting compound are the black oxid ofcoppergwolframic trioxid or tungstic acid, asbestos, the oxids ofchromium, iron, cobalt, and nickel, and the silicates of aluminium,magnesium, and zirconium.

Among the most serious of the practical difficulties which haveheretofore hindered the employment of oxid compounds as electricalconductors, especially for high-temperature work, are the extremebrittleness and fragility of the compounds, which, together with thedifficulty of attaching them to suitable terminal conductors, haveprevented their use in the thin or attenuated forms nee Iciently-attenuated form and at the same time to crack.

to give it the requisite mechanical strength, we apply it as a film orlayer upon the surface of an insulating body or core of hard refractorymaterial, to which it is made to adhere by fusion. The non-conductingcore or base provides a firm and unyielding support, both for thecoating of conducting-oxid and for the metallic terminal connections,the ends of which are preferably embedded in the conducting compound.

The accompanying drawings illustrate the device in a form in which itmay be applied practically-for example, to a cigar-lighter. This specialform is shown merely to illustrate and explain the invention, which iscapable of many other useful applications.

111 the drawings, Figure 1 represents a section on the line it o of Fig.2,which is an end view. Figs. 4 and 6 are end views showing modifiedforms of the device, and Figs. 3 and 5 are sectional Views on the linesw 00 and 'y z of Figs. 4 and 6.

Similar letters indicate corresponding parts in all the views.

A indicates the non-conducting support or core, B the superimposed layeror coating of conducting-oxid, O and O the terminal wires, the ends ofwhich are embedded in the conducting-layer B at the points 02 and e. v

The block or core A may consist of any hard refractory material to whichthe coating B can be made to adhere. To obtain the best results, itscoefficient of expansion by heat should not differ widely from that ofthe conducting-oxid; otherwise the coating is liable \Ve prefer to usefor the supporting-body A a substance of the same general nature as thecoating Bt0 wit, an oxid compoundbut in order that the path of thecurrent may be confined practically to the surface layer the material ofthe support A should have an electrical resistance Very considerablyhigher than that of the conducting compound B. Fire-clay, porcelain, andasbestos are examples of suitable materials for the support A.

The layer of conductive oxid B may be applied to the surface of thebodyA in a num ber of different ways. For example, the conductivesubstance may be laid upon the surface of the refractory block in apowdered form and fused thereon by directing an electric are upon it,after which it is cooled, so as to harden upon the surface, or it may befirst melted in a crucible and then poured over the surface of thebodyA; but the process which we consider best for general use is asfollows:

The oxids employed to form the conductor are ground in a powdered form,mixed in the desired proportions, and melted in a crucible. As thisrequires a very high temperature, it is best done in an electricfurnace. The refractory body A, held by means of a pair of tongs orother convenient means, is then dipped into the bath of moltenconductingoxid, so as to submerge as much of its surface as it isdesired to cover with the conduct-ing material and immediatelywithdrawn. A layer of the molten oxid is thus made to adhere to thesurface of the body A. On cooling the body A the adherent mass of oxidforms a hard coating or film firmly united to the base by a sort ofwelding, due probably to partial fusion of the surface of thesupporting-body.

It is found generally advantageous to heat the refractory body A nearlyto a red heat before dipping it, and also to cause the process ofsubsequent cooling to proceed somewhat slowly; but good results areoften obtained without observing these precautions.

To insure a. perfect mechanical and electrical connection between theconductingfilm B and the terminals of the conductingwires 0 and O, weprefer to attach the latter to the insulating-body A before the latteris dipped into the bath of molten oxid. As shown in the drawings, thewires 0 and O are passed through holes f and g in the insulating-blockA, and may be fastened therein by cement or other convenient means. Theends are preferably turned down, so as to extend for a short distancealong the surface of the body A, as indicated by dotted lines at d and6. When this is done, the same operation which forms theconductingcoating on the surface of the body A also embeds the ends ofthe conducting-wires in that coating, forming a strong and durableconnection.

The embedded ends of the wires 0 and C may be of copper; but as this isliable to oxidation at the point of junction we prefer to use platinum.

Then the outer ends of the leading wires C and O are connected to asource of electricity a current depending upon the electromotive forceand resistance in the circuit will flow through these wires and throughthe film of oxid B between the points d and e.

If the electromotive force and resistance are properly adjusted to eachother, a band or strip of the oxid (indicated roughly by the shadedportion of the drawing in Fig. 2) will be heated by the passage of thecurrent to incandescence, and may be applied to light a cigar, or whencarried to a sufficiently high temperature to the purpose ofillumination.

If the coating of oxid is uniformly spread over the surface of thesupporting-body, the current will naturally take the shortest path in itbetween the terminals d and 6. By means such as are illustrated in Figs.3, 4t, 5, and 6, however, the current may be made to take a moreroundabout path and to follow any prescribed course between theterminals.

In Fig. 4 the shaded portion represents a ridge on the surface of thesupporting-block A, which is dipped in the bath of molten oxid only deepenough to form a coating on the raised portion, to which the current isthere fore limited.

In Fig. 6 the shaded portion represents a groove filled with theconducting-oxid, as shown sectionally in Fig. 5, whereby a similarresult is accomplished. In this case the oxid may be melted in thegroove by the application of an electric arc to the surface, may bepoured into it, or the whole upper surface of the body A may be firstcoated and the raised portions afterward ground off, leaving the oxidonly in the groove, as is most convenient.

Other variations in the details of the combinations and processes bywhich our invention may be applied to special purposes may be readilydevised, the main elements of the combination remaining the same.

\Vithout limiting ourselves to the details shown and described, what weclaim as our invention, and desire to secure Letters Patent, is-- 1. Inan electric conducting device, the combination, with a non-conductivesupport, of a layer or film of conductive oXid applied to the saidsupport while in a fused state, substantially as described.

2. In an electric conducting device, the combination with anon-conductive support, of a superimposed layer or coating of conductiveoxid, applied to the support while fused, and metallic terminalconnections embedded in. the layer or coating, substantially asdescribed.

3. In an electric conducting device, the combination with anon-conductive support of a superimposed layer of conductive oxid,applied to the support while fused, and metallic terminal connectionspassing through the body of the support and having their ends embeddedin the conductive-oxid coating, substantially as described.

In testimony whereof we have signed our names to this specification inthe presence of two subscribing witnesses.

HENRY G. ONEILL. HORACE B. GALE.

Witnesses:

THOMAS J. CUNNINGHAM, ODEN B. ROBERTS.

